That would be correct for most mods, but NOT the hugemod. You extract it to C

rogram FilesMount&Blade . And since you're using WinRAR, it will make C

rogram FilesMount&BladehomethanatosProgramshugemodMount&Blade instead. Take the files out of each subdirectory of the extracted folder tree and put it into the right folder in C

rogram FilesMount&Blade . For example, all the files in C

rogram FilesMount&BladehomethanatosProgramshugemodMount&BladeCommonRes go into C

rogram FilesMount&BladeCommonRes . Overwrite the old ones, but remember to make backups as jackyjkchan said.
edit: Explaining the WinRAR comment: something is wierd with this file that makes the huge folder tree. Other programs can extract to the right place by extracting $file$homethanatosProgramshugemodMount&Blade to C

rogram FilesMount&Blade, but for some reason WinRAR won't. It will always extract the whole tree above that folder.